Modular landing gear

ABSTRACT

A modular aircraft landing gear assembly is disclosed having a modular landing gear bracket, connectable to an aircraft via a hinge portion, a lever for carrying a wheel, and a linkage assembly for transmitting ground loads via a spring and/or a shock absorber. The bracket comprises structure which redundant when used on an aircraft of a first type but which is necessary for use of the same type of bracket on a different type of aircraft. The modular landing gear assembly may thus provide a design platform from which landing gear assemblies can be readily designed and manufactured for use on different types of aircraft with faster and/or easier redesign and/or recertification of the aircraft landing gear assembly for such subsequently designed types of aircraft.

BACKGROUND OF THE INVENTION

The present disclosure relates to an aircraft landing gear assembly anda method of manufacturing a landing gear assembly. More particularly,but not exclusively, this invention concerns a modular aircraft landinggear assembly.

A conventional landing gear assembly comprises a primary landing gearleg having a hydraulic shock absorber (an oleo strut) which, whendeployed, extends vertically, or close to vertical, from the aircraftbody or wing to the wheels on the ground. The majority of the verticalloads are transmitted from the wheels into the aircraft via the leg. Thesingle leg typically carries two, four or six wheels. A landing gearassembly for one type of aircraft is typically unsuitable for use withan aircraft having a significantly higher maximum take-off weight(MTOW). Thus, if it is desired to take an existing aircraft design andmodify it to have a significantly higher maximum take-off weight,significant redesign work would typically be required of the landinggear assemblies. The total number of wheels the aircraft needs may haveto increase. Given that the conventional landing gear configurations aredifficult to adapt for use with an odd number of wheels, and given thatthere are typically an even number of main landing gear legs (disposedsymmetrically about the longitudinal vertical mid-plane of theaircraft), increasing the MTOW of an aircraft by a certain amount willcause the number of wheels to increase by four, causing a significantjump in mass for what might be a relatively modest jump inpassenger/cargo capacity for the aircraft design. An alternativeapproach would be to provide for an additional two-wheel main landinggear at the aircraft centreline, but such a solution also addssignificant mass.

Also, redesigning landing gear for use on an aircraft so that the newlydesigned aircraft has an extended wing tip, as might be required forbetter aerodynamic performance for example, is difficult to achieve withthe conflicting requirements that may arise for a wing mounted landinggear. The shape of the wing may require the wheels to be locatedsignificantly behind (aft) the rear spar of the wing via which thelanding gear is mounted. However, the oleo strut may need to be arrangedto transmit loads in a direction that is substantially parallel with itsaxis, thus preventing the oleo strut from being angled too far beyondvertical (typically being angled at 6 degrees or less).

When designing or redesigning a landing gear assembly for an aircraft,conventional wisdom is to seek to keep the mass of the landing gearassembly as low as practically possible.

The present invention seeks to mitigate one or more of theabove-mentioned problems. Alternatively or additionally, the presentinvention seeks to provide an improved aircraft landing gear assembly.Alternatively or additionally, the present invention seeks to provide adesign platform from which multiple different landing gear assembliesmay be readily designed and/or manufactured.

SUMMARY OF THE INVENTION

The present invention provides according to an aspect of the invention amodular aircraft landing gear assembly, wherein the modular aircraftlanding gear assembly comprises a modular landing gear bracket, which inuse is connected to the aircraft via a hinge, for example, for rotatingthe aircraft landing gear assembly between a deployed position and astowed position. The bracket is arranged to carry one or more wheels,preferably at least two. A lever, which in use carries at least onewheel, is rotatably mounted to the bracket. The axis of rotation of thelever may for example be parallel (or close to parallel) to the axis ofa wheel carried by the lever in use. The modular aircraft landing gearassembly also includes a linkage assembly, which may for example bepivotally mounted the bracket, which linkage assembly in use transmitsat least some of the ground load via at least one of a spring and ashock absorber. The structure of the bracket itself may be substantiallyrigid, for example thus providing negligible shock absorption orresilience (springiness). The modular landing gear bracket alsocomprises redundant structure, which is surplus to requirements foroperation of the aircraft on which the aircraft landing gear assembly isto be used. The redundant structure may for example comprise one or moreof an additional mounting point, for example for a part or portion of alinkage assembly to be mounted on the bracket when the same design (orsubstantially the same design) of bracket is used on a differently sizedaircraft. Such a redundant or additional mounting point of the bracketmay be associated with load carrying mass of the bracket (e.g. fortransmitting at least some of the ground load from the wheels into theaircraft) which could also be considered as redundant. The redundantstructure may, for this or other reasons, include additional mass.

Thus, in accordance with embodiments of the invention, there is provideda modular aircraft landing gear assembly, which can be reused ondifferent types of aircraft (for example, having a longer fuselageand/or a different MTOW) without the need for significant redesign ofthe aircraft landing gear assembly for the subsequently designedaircraft. The certification of the aircraft landing gear assembly forthe subsequently designed aircraft may also be made simpler and/orquicker.

The bracket may be shaped such that it extends from a hinge portion to afirst mounting point, for receiving a ground load from one or morewheels, in use. Such a hinge portion may be configured for mounting thebracket for rotation relative to a landing gear bay. The modular landinggear bracket may include a second mounting point at a fore location ofthe hinge portion and a third mounting point at an aft location of thehinge portion. The bracket may have two mounting points only on thehinge portion for mounting for rotation relative to the aircraft. Eachmounting point on the hinge portion may in use be associated with apintle.

The bracket may thus be configured so that the ground load received atthe first mounting point is, in use, transferred into aircraft structure(e.g. into the wing, fuselage, or other main structure of the aircraft)via the second mounting point and the third mounting point. In thefore-to-aft direction, the second mounting point may be the firstmounting point for mounting the bracket relative to the landing gear bayvia the hinge portion, and the third mounting point may be the last.

The bracket may include structure for receiving a second aircraft wheel,such a structure for example being the same lever as that which carriesthe first wheel. Such a structure may for example be a further lever,for example similar to the lever carrying the first wheel. When twolevers are provided, they may be mounted to the bracket at the samemounting point. One of the levers may be positioned behind the other, inthe fore-aft direction. The linkage assembly may be pivotally mountedvia a fourth mounting point of the bracket. The linkage assembly may bemodular in design, for example in that different configurations oflinkage assemblies may be used in relation to the same design ofbracket, to adapt the bracket for use for different purposes (e.g. ondifferent designs of aircraft).

The modular aircraft landing gear assembly may be configured for atwo-wheel configuration. In such a case, the redundant structure mayfacilitate reconfiguring the modular aircraft landing gear assembly foruse with more wheels, for example with a three-wheel configuration orfour-wheel configuration. The two-wheel configuration may be one inwhich the first and the second wheels are in line with each other (e.g.a tandem configuration).

The lever may have a first end which is rotatably mounted to the bracketat the first mounting point and a second end for receiving a firstaircraft wheel. The second end of the first lever may be positionedforward of the first end. When a second lever is provided, it may have afirst end which is rotatably mounted to the bracket (for example at, ornear, the first mounting point) and a second end, positioned rearward ofthe first end, for receiving the second aircraft wheel. The second levermay carry a trailing wheel. (Of course, when there is only onelever—i.e. a single first lever—the first lever may be arranged suchthat it carries a trailing wheel. (The first lever may have a first endwhich is rotatably mounted to the bracket and a second end, positionedrearward of the first end, for receiving a wheel.) It may be that theaircraft wheel of the first lever is, in use with the aircraft on theground, located to one side in an outboard direction of the mid-plane ofthe bracket (and/or for example to one side in the outboard direction ofthe first lever). It may be that the second lever is configured toreceive the second aircraft wheel so that it is positioned in-line withthe first wheel (for example also in an offset and/or outboardposition). It may be that the first and second levers are arranged tocarry between them two wheels in a diagonal arrangement, such that inuse with the aircraft on the ground, the aircraft wheel of one of thefirst and second levers is located to one side in an outboard directionof the mid-plane of the bracket and the other aircraft wheel (i.e. ofthe other of the first and second levers) is located to the oppositeside of the bracket (i.e. to one side in an inboard direction of themid-plane of the bracket). In embodiments of the invention, the use of abracket and two wheels in a tandem arrangement or in a diagonalarrangement, the wheels being offset from the bracket, can enable anefficient geometry for stowage of the aircraft landing gear assembly ina landing gear bay of the aircraft. A diagonal arrangement may have anadvantage in that the first and second levers may be able to have thesame shape as a result of the rotational symmetry of the levers andassociated wheels on the landing gear.

The redundant structure of the bracket may be provided to enable thebracket to carry three wheels, for example two being arranged in diabloconfiguration (e.g. arranged to rotate about a common axis) and onebeing arranged either forward of or behind the two wheels. There may betwo levers for this purpose. For example, one of the first lever and thesecond lever is configured to be able to carry two wheels in a diabloconfiguration, and the other of the first lever and the second lever isconfigured to be able to carry a single wheel. It may be that the singlewheel is positioned, when viewed in the direction of travel on theground, in between the two wheels of the diablo configuration. It may bethat the single wheel is positioned in-line with the bracket. It may bethat the two wheels of the diablo configuration are positioned such thatone wheel is outboard of the lever and the other wheel is inboard of thelever.

In relation to a three-wheel configuration, there may be a linkageassembly (or assemblies) and associated spring(s) and/or shockabsorber(s) for the two wheels which is/are bigger, stiffer and/or havemore parts than a linkage assembly (or assemblies) and associatedspring(s) and/or shock absorber(s) for the single wheel. There may be alinkage assembly (or assemblies) and associated spring(s) and/or shockabsorber(s) for a three-wheel configuration which is/are bigger, stifferand/or have more parts (for example, an extra linkage assembly) than alinkage assembly (or assemblies) and associated spring(s) and/or shockabsorber(s) for a two-wheel configuration. The bracket may be sodesigned that substantially the same design of bracket is able to beused both with a two-wheel configuration and also a three-wheel (ormore) configuration with little or no modifications to the shape and/orsize of the bracket. It may be that modifications (of any significanttype for example) are only necessary in relation to the number, sizeand/or configuration of the link assembly/assemblies, the spring(s)and/or shock absorber(s). There may be a respective shock absorberassociated with each respective wheel.

One or more parts of such linkage assembly/assemblies provided for thethree-wheel configuration may be absent from the modular aircraftlanding gear assembly, when used for carrying two wheels.

The ability of the modular aircraft landing gear assembly to beconverted between a two-wheel configuration and a three-wheelconfiguration, allows (in a much easier way) a smaller step-wise changein the total number of wheels (and therefore the additional weightprovided by the extra wheels and associated parts and structure) than ispossible with conventional landing gear design practices which typicallyrely on each main landing gear (MLG) having an even number of wheels.Such a possibility allows a more efficient step-wise change in mass, forexample from a single aisle lightweight aircraft with two 2-wheel MLGsto a longer and heavier variant with two 3-wheel MLGs. Such apossibility might alternatively/additionally allow for a lighter and/orshorter variant as between a long-range heavy aircraft having two4-wheel MLGs to a lighter variant having two 3-wheel MLGs.

The modular aircraft landing gear assembly may include a balance arm,for example rotatably mounted on the bracket (e.g. via a middle pivotpoint) for receiving load from both a fore lever carrying one or morewheels and an aft lever carrying one or more wheels. The arm may forexample have a fore end pivot point connected to the first lever via oneor more link members which transmit loads received from the first leverand/or the arm may have an aft end pivot point connected to the secondlever via one or more link members which transmit loads received fromthe second lever. The balance arm may have a middle pivot point which isoffset from the position midway between the fore end pivot point and theaft end pivot point. Having a balance arm, offset in this manner, mayallow differently sized loads to be better distributed by the wheelsand/or bracket and/or into the aircraft. The middle pivot point may bepositioned closer to whichever of the fore and aft pivot points transmitthe greater ground loads and/or are associated with the lever whichcarries the greater number of wheels. It may be that there is one leverthat is configured to transmit significantly greater ground loads thanthe other. It may be that in use one lever transmits significantlygreater ground loads than the other, but the two levers have a similarload bearing capacity, such that at least one of the levers hasredundant mass, in use. In embodiments of the invention, the balance armis associated with (connected to, possibly via one or more links) acompliant device, such as a shock absorber or dampener.

As mentioned above, the modular aircraft landing gear assembly mayinclude one or more shock absorbers. The one or more shock absorbers maybe the principal means by which dampening of the landing gear wheels isprovided. There may be a single principal shock absorber provided perlever (on which the wheel(s) are mounted). There may be a first shockabsorber which transmits loads from the first lever, for example withoutany intervening structure that functions as a spring or shock absorber.There may be one or more link members (for example of the linkageassembly) which are linked to the first shock absorber such that, inuse, the link member(s) transmit(s) loads from the first lever. Theremay be a second shock absorber which transmits loads from the secondlever, for example without any intervening structure that functions as aspring or shock absorber. There may be one or more link members (forexample of the linkage assembly) which are linked to the second shockabsorber such that, in use, the link member(s) transmit(s) loads fromthe second lever. One of the first and second shock absorbers may be alow pressure shock absorber. One (e.g. the other) of the first andsecond shock absorbers may be a high pressure shock absorber. Themodular aircraft landing gear assembly may therefore include two or moreshock absorbers, which collectively function as a multi-stage shockabsorber system as a result of the differently pressured shockabsorbers. There may be advantages in being able to segregate the highand low pressure stages of such a shock absorber system by providingthem by means of separate shock absorbers. In embodiments of theinvention, high and low pressure shock absorbers are linked via abalance arm.

It within the scope of the present invention for a variant of thebracket, or for the bracket of the aircraft landing gear assembly of theinvention, to be raked at an angle to the vertical. The provision of alinking assembly may assist in the provision of a raked bracket. Thelinking assembly may allow a non-vertical, or angled shock absorber forexample. The raked nature of the bracket may be such that, in use, whenthe aircraft is static and on the ground the first mounting point on thebracket (at which a lever is mounted) is located aft of the thirdmounting point (an aft mounting point of the hinge portion of thebracket, possibly the mounting point of the hinge portion that isfurthest aft). The raked nature of the bracket may be such that, in use,when the aircraft is static and on the ground, the rake angle of thebracket is eight degrees or higher (e.g. greater than ten degrees). Incertain embodiments, the rake angle of the bracket is defined by theangle to the vertical of the notional line extending from the firstmounting point to the rearmost mounting point of the hinge portion (e.g.which may be the third mounting point). Having a design platform thatallows for a raked bracket in this way enables embodiments of theinvention with advantageous geometries for the use on an aircraft withwings having extended wingtips.

The linkage assembly may comprise a loading point which is movablerelative to the hinge portion of the bracket. The loading point may forexample receive ground loads from a lever carrying a wheel, when in use.The linkage assembly may comprise a spring system. The spring system maybe configured to apply a resilient biasing force acting against theground loads. The spring system may be configured to apply a resilientbiasing force so that, during application of an increasing load, thespring rate of the spring system changes in dependence on the load beingtransmitted. The spring rate of the spring system may change from afirst spring rate to a second spring rate, for example, the secondspring rate being less than the first spring rate. As the applied load(e.g. from ground loads) against the resilient biasing force of thespring system is further increased, the spring rate of the spring systemmay change from the second spring rate to a third spring rate, the thirdspring rate being greater than the second spring rate, for example. Thespring system may comprise a first spring element and a second springelement. A spring rate of the second spring element may be less than aspring rate of the first spring element. The loading point of thelinkage assembly may be connected to the second spring element via thefirst spring element. The first spring element may be rotationallymounted to the bracket at the fourth mounting point mentioned above. Thebracket may have a stop (which may be integrally formed, or provided ondetachably mounted structure) that is configured to limit rotation ofthe linkage assembly beyond the stop. The second spring element may beconfigured to apply a preload. The bracket may have first and secondstops configured to limit an angular range of rotation of the linkageassembly. The first spring element may comprise a leaf spring. Thesecond spring element may comprise a leaf spring.

The modular landing gear bracket may include a fifth mounting point, forexample, for the mounting of a further linkage assembly. Such a furtherlinkage assembly may be positioned either fore or aft of the linkageassembly pivotally mounted via the fourth mounting point.

The bracket may carry substantially all of the vertical ground loads (orat least 80% of them) from its associated wheels into the aircraft. Someside loads, torsion loads, shear loads or the like may be carried bystructure that is additional to the bracket. The bracket may have twoprincipal load paths, comprising a fore load path and an aft load path.The bracket may be provided in the form of a frame structure. The framestructure may be an open frame. The main structure of the bracket may beprovided by two, preferably similarly shaped, parts (e.g. plates), forexample being in the form of two parallel spaced apart plates.

The landing gear assembly of the present invention may, or may not, beprovided with one or more wheels mounted on the landing gear.

The present invention also provides a kit of parts for assembling themodular aircraft landing gear assembly according to any aspect of theinvention as described or claimed herein. The kit may comprise one ormore of the above mentioned modular landing gear brackets. The kit maycomprise one or more of the above mentioned levers. The kit may compriseone or more of the above mentioned link assemblies. The kit may compriseone or more of a link member, the above mentioned spring or springsystems and the above mentioned shock absorber(s) for forming a linkageassembly.

The present invention also provides an aircraft including a modularaircraft landing gear assembly according to any aspect of the inventionas described or claimed herein. The aircraft may be a single aisleaircraft. The aircraft may be a long range aircraft, having a range ofmore than 3,000 miles for example. The aircraft may be a passengeraircraft, for example an aircraft configured to carry more than 50passengers, for example more than 100 passengers, possibly at least 200passengers For the purposes of the present specification the termcommercial passenger aircraft also covers aircraft of an equivalent sizeconfigured for cargo and/or used on a non-commercial basis. The aircraftmay have a maximum take-off weight (MTOW) of at least 20 tonnes,optionally at least 40 tonnes, and possibly 50 tonnes or more. Theaircraft may have an operating empty weight of at least 20 tonnes,optionally at least 30 tonnes, and possibly about 40 tonnes or more. Thelength of the aircraft is preferably greater than 25 m, and may begreater than 30 m. The length of the aircraft may be greater than 40 m.

There is also a method of manufacturing a landing gear assembly asdefined in the claims and/or as described in further detail below. Themethod may include designing both (a) a first aircraft landing gearassembly for a first aircraft, and (b) a second aircraft landing gearassembly for a second aircraft. The first aircraft may have a fuselageof a first length and the second aircraft may have a fuselage of asecond longer length, for example longer by at least 5 m and possibly byat least 10 m. The first aircraft may have a first MTOW and the secondaircraft may have second higher MTOW, for example higher by at least 5tonnes, and possibly higher by at least 10 tonnes. It may be that thefirst aircraft landing gear assembly is either a two-wheel tandemlanding gear assembly or a two-wheel diablo landing gear assembly. Itmay be that the second aircraft landing gear assembly has one more wheelthan the first aircraft landing gear assembly (i.e. a step from two tothree, or a step from three to four wheels per MLG). There may befeatures or mass of the first aircraft landing gear assembly that areredundant for the purpose of operation of the first aircraft but whichare used as features or mass of the second aircraft landing gearassembly. Such redundant features and/or redundant mass as are providedon the first aircraft landing gear assembly may have a combined massthat is greater than 0.1% of the total mass (possibly greater than 0.5%,and possibly greater than 1%) of the first aircraft landing gearassembly (excluding the wheels, brakes, and brake systems). Suchredundant features and/or redundant mass as are provided on the firstaircraft landing gear assembly may have a combined mass that is greaterthan 1 Kg, possibly greater than 5 Kg, and optionally greater than 10Kg. The first aircraft may be a single aisle aircraft. The secondaircraft may be a long range aircraft. The second aircraft landing gearassembly may have a different topology/geometry in relation to how thewheels are mounted on the landing gear. For example, it may be that thefirst aircraft landing gear assembly is a two-wheel tandem landing gearassembly and the second is a two-wheel diablo landing gear assembly. Itmay be that the first aircraft landing gear assembly is a two-wheeldiablo landing gear assembly and the second is a two-wheel tandemlanding gear assembly. It may be that the second aircraft landing gearassembly has three or more wheels, whereas the first aircraft landinggear assembly has only two. The first aircraft landing gear assembly maycomprise a modular load-bearing frame, modular load-bearing bracket orthe like. It will be appreciated that one of the first and secondaircraft landing gear assemblies may be a design modification of theother, in that there need not be any wholescale redesign of the earlierdesign in the creation of the later design. For example, one of thefirst and second aircraft landing gear assemblies may be a designmodification of the other utilising a common generic design model. Thecommon generic design model may utilise the same modular load-bearingframe, modular load-bearing bracket or the like. The common genericdesign model may utilise the same separation of locations of themounting points of the aircraft landing gear to the aircraft. It may bethat the load-bearing frame of the second aircraft has the same geometryas the load-bearing frame of the first aircraft but is scaled up. It maybe that the load-bearing frame of the second aircraft has the same shape(and, for example, also the same overall size) as the load-bearing frameof the first aircraft but is strengthened by use of extra mass in thestructure of the load-bearing frame.

It will of course be appreciated that features described in relation toone aspect of the present invention may be incorporated into otheraspects of the present invention. For example, the method of theinvention may incorporate any of the features described with referenceto the apparatus of the invention and vice versa.

DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described by way ofexample only with reference to the accompanying schematic drawings ofwhich:

FIG. 1 is a perspective view of part of an aircraft showing a modularaircraft landing gear assembly according to an embodiment of theinvention;

FIG. 2 is a sectional side view of the aircraft landing gear assembly ofFIG. 1;

FIG. 3 is a side view of an aircraft which may incorporate a landinggear assembly of an embodiment of the invention;

FIG. 4 is a perspective view of part of an aircraft showing a modularaircraft landing gear assembly according to a further embodiment of theinvention, in which the wheels are offset to one side;

FIG. 5 is a perspective view of part of an aircraft showing a modularaircraft landing gear assembly for a three-wheel configuration accordingto an embodiment of the invention,

FIG. 6 is a sectional side view of the aircraft landing gear assembly ofFIG. 5;

FIG. 7 is a sectional side view of an aircraft showing a modularaircraft landing gear assembly according to a further embodiment of theinvention using a shock absorber and an associated offset balance arm;

FIG. 8 is a sectional side view of an aircraft showing a modularaircraft landing gear assembly according to a further embodiment of theinvention using segregated high-pressure and low-pressure shock absorberin combination;

FIG. 9 is a sectional side view of an aircraft showing a modularaircraft landing gear assembly according to a further embodiment inwhich a raked bracket is used;

FIG. 10 is a perspective view of a modification to the embodiment shownin FIG. 1;

FIG. 11 is a perspective view of a further modification to theembodiment shown in FIG. 1; and

FIG. 12 shows a flowchart of the steps of a method of manufacturing anaircraft landing gear assembly according to an embodiment of theinvention.

DETAILED DESCRIPTION

FIGS. 1 and 2 show schematically an aircraft landing gear assembly 10suitable for use on an aircraft 12 (such as that also shown in FIG. 3).The fore direction is shown in FIG. 1 with the arrow labelled F. Theaircraft landing gear assembly comprises a bracket and spring assemblyarrangement for transmitting ground loads, which has various potentialdesign advantages as compared to prior landing gear assemblies whichtransmit the majority of ground loads utilising a single elongatelanding gear leg with an integrated shock absorber (referred to in theart often as an oleo landing gear design). The bracket acts as the mainfitting for the aircraft landing gear assembly.

The landing gear assembly of FIG. 1 includes a bracket 14 extending froma hinge portion 18 to a first mounting point 20 for mounting one or morewheels 22 via one or more pivoting levers 16. The hinge portion 18allows for mounting of the bracket 14 for rotation relative to a landinggear bay, so that the landing gear assembly 10 may move between a stowedposition (in the landing gear bay) to a deployed position (for landing,taxiing and take-off), as shown in FIGS. 1 and 2. In the deployedposition, the first mounting point 20 receives ground loads from thewheels 22 when the aircraft's weight is supported on the ground. Theremay also be a side-stay assembly (not shown) for reacting lateral loadson the landing gear which transmit loads into the aircraft at a furtherlocation. It will be noted that the perspective views in the Figuresshow different details from that shown in the side views. For example,FIG. 2 shows a hinge tube 19, not shown in FIG. 1, which passes loadsfrom the bracket into the aircraft structure 12 via two outer mountingpoints (not labelled in FIG. 1).

The bracket 14 has a second mounting point 24 at a fore location of thehinge portion 18 and a third mounting point 26 at an aft location of thehinge portion, for mounting of the bracket 14 to aircraft structure, inthis case to the fuselage of the aircraft. In FIG. 1, it will be seenthat there are two further locations, one forward of the second mountingpoint 24 and one aft of the third mounting point 26, for mounting of thebracket 14 to aircraft structure, there thus being four locations intotal. It will also be seen from FIG. 1 that the bracket 14 comprisestwo parallel spaced-apart plates, each having a (very generally)triangular shape (the base of the triangle corresponding to the hingeportion and the first mounting point 20 being at or close to apex of thetriangle, opposite the base).

With reference to FIG. 2, there are two levers 16, each being rotatablymounted at one end to the bracket 14 at the first mounting point 20 andeach receiving an aircraft wheel 22 at the opposite end. Each lever 16is associated with a spring assembly 130, which may be considered asbeing, or forming part of, an independent modular suspension system forthe wheel(s) carried by the lever with which the spring assembly 130 isassociated. The wheel 22 is mounted for rotation about an axis 30. Thelever 16 rigidly connects between three points: the first mounting point20, the wheel axis 30, and an end 135 b of a linkage 135 (the other end135 a of which pivotally connects to an end of a first spring element131 which forms part of the spring assembly 130, as is explained infurther detail below). In use, the load from the wheel 22 is applied toa loading point 120 via the lever 16 and the linkage 135.

The spring assembly 130 may comprise one or more spring elements, thenumber being chosen in dependence on the requirements of the landinggear/aircraft. One or more shock absorbers, dampeners or other means fordissipating motion are incorporated into the spring assembly orsuspension system to absorb or dampen shock impulses applied to thespring assembly or suspension system in use.

The nature of the bracket, the separate levers, the separate springassemblies and associated linkages provides a design platform thatfacilitates the design of landing gear assemblies for different aircraftusing a modular design approach. Many landing gear designs for modernpassenger aircraft having a MTOW of more than, say, 20 tonnes featureretractable landing gear assemblies. Each landing gear assembly(according to such a prior art aircraft design) typically comprises alanding gear leg in the form of a hydraulic strut which is configured tosupport the majority of the vertical ground loads when the aircraftlands, takes-off or performs ground manoeuvres. (It will of course beappreciated that such vertical struts also react non-vertical loads inuse too.) If a first aircraft is designed using a landing gear carryinga certain number of wheels, and that design of aircraft is utilised asthe starting point for the design of a future aircraft having adifferent length and a different MTOW (for example by starting withstretching or shrinking the length only of the fuselage), it is oftenthe case that a different number of wheels will be required of at leastone of the landing gear assemblies and/or a differently sized hydraulicstrut will be required. Reconfiguring the landing gear assembly to besuitable for a resized aircraft can thus involve a significant redesignof the landing gear assembly (or, effectively, a new design of landinggear assembly). If the same or similar landing gear assembly could bere-used, or reconfigured for a new purpose without requiring anyfundamental design changes, then not only could the design process bespeeded up, but also certification of the aircraft could be made easierand/or faster.

Designing a landing gear assembly using a modular aircraft landing gearassembly such as that shown in FIGS. 1 and 2, may result in one designof landing gear having redundant structure, which is however fullyutilised in a different aircraft (for example, one having a longerfuselage or a higher MTOW). It may be that such redundant structure addsredundant mass in the landing gear assembly of one aircraft on which thebracket is used, but this may be relatively minor. Furthermore, anydisadvantage associated with such modest increase in mass, can be morethan offset by the potential advantages gained by the simplification ofthe redesign and/or recertification needed for the aircraft landing gearassembly for the subsequently designed aircraft. Costs associated withmanufacturing may also be reduced, when utilising such a modular design.The bracket 14 of FIGS. 1 and 2 comprises redundant structure, which issurplus to requirements for operation of the aircraft on which theaircraft landing gear assembly is to be used. In this embodiment, thereis redundant structure provided as a result of additional mountingpoints 28 r on the bracket 14, such redundant mounting points being fora linkage assembly/spring assembly, which is not used on the aircraftshown but which could be utilised on a different set-up for a differentaircraft to assist in the transmitting of some of the ground loads. Thebracket 14 itself is larger (and therefore more massive) than requiredfor the operation of the aircraft on which it is installed, so that itis also suitable for use on heavier aircraft or on a landing gearassembly which must be capable of sustaining higher ground loads.

The spring assembly 130 is similar to that disclosed in the embodimentsof GB 2 568 742, the contents of which being incorporated by referencethereto. However, a brief explanation of the spring assembly 130 andother subject matter covered by GB 2 568 742 is also included in thedescription, which now follows.

Each spring assembly 130 includes first spring elements 131 and secondspring elements 132. The first spring elements 131 form part of alinkage assembly transferring loads from the wheel 22 via its lever 16into the bracket 14. The first spring elements 131 are mounted on thebracket at a fourth mounting point 28 of the bracket, permittingpivoting movement of the first spring elements 131 relative to thebracket.

The second spring element 132 is associated with a preload applicator134 (described below). The spring assembly 130 comprises a loading point120 for receiving ground load from the wheel(s) in use. The loadingpoint 120 in this embodiment is at the joint between the linkage 135 andthe first spring element 131. The loading point 120 is thus movablerelative to the hinge portion 18. The spring assembly 130 is configuredto apply a resilient biasing force to the loading point 120 to opposemovement of the loading point 120 relative to the hinge portion 18. Inthis embodiment, the loading point 120 is movable towards and away fromthe hinge portion 18, and the spring system or spring assembly 130 isconfigured to apply a resilient biasing force to the loading point 120to oppose movement of the loading point 120 towards the hinge portion18. During application of an increasing load to the loading point 120against the resilient biasing force of the spring assembly 130, a springrate of the spring assembly 130 changes from a first spring rate to asecond spring rate, the second spring rate being less than the firstspring rate. The first spring rate can therefore be a relativelymoderate spring rate for getting load onto the wheel(s), which can helplessen or avoid skidding and to help improve braking drag. The second,lower spring rate can thereafter help provide a soft ridecharacteristic. In this embodiment, the movement of the loading point120 is towards the hinge portion 18 during application of the increasingload to the loading point 120, such as during a landing procedure orevent. In this embodiment, the spring assembly 130 is also configured sothat, if the load applied to the loading point 120 against the resilientbiasing force further increases, the spring rate of the spring assembly130 changes from the second spring rate to a third spring rate, thethird spring rate being greater than the second spring rate. This thirdspring rate can help to react loads in high-descent-rate landings,and/or may help to improve lateral stability when the aircraft to whichthe landing gear is mounted is taxiing or otherwise turning on theground. The third spring rate may be substantially equal to the firstspring rate in certain embodiments, and may be less than (or greaterthan) the first spring rate in others.

The spring elements 131 and 132 each comprise a leaf spring. Use of leafsprings can enable the spring assembly 130 to begin to compress as soonas a load is applied to the loading point 120. That is, the springassembly 130 may be considered to have a zero, or substantially zero,break-out load. This can facilitate weight-on-wheels detection, such asto determine whether the landing gear 10 (and the aircraft 12 to whichit is mounted) has landed.

In this embodiment, the first spring element 131 is coupled to thesecond spring element 132 via a link 133. A first end of the link 133 ispivotally coupled to the first spring element 131, and a second end ofthe link 133 is pivotally coupled to the second spring element 132. Inother embodiments, the link 133 may be omitted. In some suchembodiments, the first spring element 131 may be pivotally coupleddirectly to the second spring element 132. The spring elementsthemselves may be considered as links which form the overall linkageassembly.

The bracket 14 of this embodiment has a first stop 141 and a second stop142, which together are configured to limit an angular range of rotationof the first spring element 131 about the mounting point 28. The firststop 141 limits rotation during the application of the increasing loadto the loading point 120, whereas the second stop 142 limits rotationduring removal or reduction of the load. One end of the second springelement 132 is rotationally mounted to the bracket 14 at a furthermounting point 144.

The preload applicator 134 of the spring assembly 130 of this embodimentis provided for applying a preload to the second spring element 132 andthus apply a preload to the first spring element 131, to bias the firstspring element 131 away from the first stop 141 of the bracket 14. Thus,when increasing load is applied to the loading point 120 from the wheel22 rotational movement of the first spring element 131 is caused aboutthe mounting point 28 in one rotational direction, whereas the preloadbiases the first spring element 131 to move in the opposite rotationaldirection.

For some designs of landing gear, the spring assembly 130 may compriseone first spring element 131 and plural second spring elements 132 (forexample such that a combined spring rate of the plural second springelements 132 is less than the spring rate of the first spring element131). In still further embodiments, the spring assembly 130 may compriseplural first spring elements 131 and one second spring element 132 (forexample, the spring rate of the second spring element 132 being lessthan the combined spring rate of the plural first spring elements 131).

The loads that are passed from the bracket and/or the hinge tube 19 intothe aircraft are shown schematically by the vertical arrows 39, 40, 42,43 at the top of FIG. 2. In other embodiments, the bracket 14 may beshaped to extend as far as the loading points indicated by arrows 40 and42. In this embodiment, there are two tubular attachments 19, one eachat the forward and aft attachment points. These tubular elements 19 areeach connected in a rotational sense only (i.e. about the retractionaxis) to the (smaller) bracket 14 (as shown in FIG. 1) by a rotatablecoupling (not shown in FIG. 1) shown in FIG. 2 as an inverted “U” 45.The loads into the airframe structure are therefore via multiple(smaller) load paths, thus spreading the load more evenly into theaircraft fuselage. The loads transmitted from the mounting points 20 and28 via the bracket 14 into the airframe (via the second and thirdmounting points 24, 26) are shown by the smaller “up” arrows 39, 43. Theloads transmitted via the second spring elements 132 are transmitted viathe fore and aft rotatable couplings 19 into the outer attachment points(as represented by the larger arrows 40, 42 in FIG. 2), and to someextent into the inner two load point (via points 24, 26).

As mentioned above, the embodiment shown in FIGS. 1 and 2 may be used asa modular aircraft landing gear assembly design platform, enabling thedesign and manufacture of different configuration of landing gearassemblies, each being configured for use on an aircraft type within afamily of aircraft designs differing from one another, for example, byMTOW, length of aircraft, and/or load capacity. Such differentdesigns/configurations of landing gear assemblies are illustrated in theaccompanying Figures. Alternatively, any of those differentdesigns/configurations of landing gear assemblies as illustrated in theother Figures may be used as the base design or platform from whichother different designs/configurations of landing gear assemblies arecreated. Alternatively, a non-illustrated landing gear assembly may beused as the base design or platform from which the other differentdesigns/configurations of landing gear assemblies are created.

FIG. 4 shows a landing gear assembly according to an embodiment similarto that shown in FIGS. 1 and 2. Like reference numerals are used forlike parts, but adding 2000 to the numbers used in FIGS. 1 and 2. Themain differences between the two embodiments will now be described. Thelanding gear 2010 has two levers 2016 each carrying one wheel 2022 on anaxle that is located to one side, in an outboard direction, of thebracket 2014 (and also in a position located to one side, in an outboarddirection, of the lever). The wheels 2022 are arranged in a tandemoffset configuration. The profile of the landing gear assembly 2010 inthe direction of flight is therefore relatively slim in the span-wisedirection, and has a geometry and size that is able to make very gooduse of the space available when stowed. The landing gear bay can thus bemade smaller and/or include space for other additional systems of partsof the aircraft. Such a configuration may be particularly suitable for alanding gear that is required to be stowed under the cabin floor.

In an alternative embodiment to FIG. 4, the two wheels could be arrangedon opposite sides of the bracket, one inboard and one outboard—in adiagonal arrangement. This may also enable the landing gear to be moreefficiently shaped, for example, enabling a belly fairing under thelanding gear when stowed to be smaller or better shaped.

Thus, the subject matter embodied by FIG. 4 and the above-describedalternative may be described in more general terms as being an aircraftlanding gear assembly comprising a, preferably modular, landing gearbracket, on which a first lever and a second lever are mounted, forreceiving wheels mounted off-centre with respect to the bracket(preferably to one side of the bracket, e.g. one or both offset to oneside in the outboard direction). There are various preferred featuresrelating to this generalised subject matter which will now be described.The modular landing gear bracket extends from a hinge portion to a firstmounting point, the first mounting point being for receiving a groundload from one or more wheels, in use. The hinge portion is configuredfor mounting the bracket for rotation relative to a landing gear bay.The bracket includes a second mounting point at a fore location of thehinge portion and a third mounting point at an aft location of the hingeportion. The bracket is configured so that the ground load received atthe first mounting point is, in use, transferred into aircraft structure(for example wing or fuselage) via the second mounting point and thethird mounting point. The first lever has a first end which is rotatablymounted to the bracket at the first mounting point and a second end,positioned forward of the first end, for receiving a first aircraftwheel. Similarly, the second lever has a first end which is rotatablymounted to the bracket at the first mounting point and a second end,positioned rearward of the first end, for receiving a second aircraftwheel. The second aircraft wheel may be positioned in-line with thefirst wheel. One of the first wheel and the second wheel may be receivedin a position located to one side in an outboard direction of themid-plane of the bracket; and/or in a position located to one side in anoutboard direction of the mid-plane of the second lever. The secondaircraft wheel may be positioned on the opposite side of the bracketfrom the first wheel (e.g. one outboard and on inboard). The aircraftlanding gear assembly may be configured to carry two wheels only.

FIGS. 5 and 6 shows a landing gear assembly according to an embodimentsimilar to that shown in FIGS. 1 and 2. Like reference numerals are usedfor like parts, but adding 3000 to the numbers used in FIGS. 1 and 2.The main differences between the two embodiments will now be described.The landing gear 3010 has two levers 3016 which between them carry threewheels 3022. In this embodiment, the fore wheel 3022 f is mounted suchthat it is arranged centrally (in the span-wise direction) relative tothe bracket. The centre plane of the wheel 3022 f—such a plane havingthe wheel axis as its normal—is substantially coplanar with thecorresponding centre plane of the bracket (or at least, the bracket 3014and wheel 3022 f are so arranged that the main load bearing structure ofthe bracket extends to either side of the centre plane of the wheel).The central mounting of this fore wheel 3022 f is readily achieved as aresult of the spaced apart parallel plates that form the bracket 3014.The aft wheels 3022 a behind the fore wheel 3022 f are in a diabloarrangement (axes lying on a common notional line), with one aft wheel3022 a being located to one side in an outboard direction of the bracket3014 (and also in a position located to one side in an outboarddirection of the lever 3016) and the other aft wheel 3022 a beinglocated to the other side (i.e. in an inboard direction) of the bracket3014 (and also in a position located to one side in the inboarddirection of the lever 3016).

A bigger spring assembly is associated with the two wheels than isprovided for the single wheel (this need not be twice the size however).With reference to FIG. 6, the fore spring assembly 3130 f associatedwith the single fore wheel 3022 f has a first spring element 3131 f inthe form of a single leaf spring and a second spring element 3132 f alsoin the form of a single leaf spring. The aft spring assembly 3130 aassociated with the dual wheels 3022 a has two first spring elements3131 a in the form of two leaf springs arranged in parallel and a secondspring element 3132 a also in the form of two leaf springs arranged inparallel.

In an alternative embodiment, a separate spring assembly is associatedwith each of the three wheels (the two spring assemblies associated withthe one lever may each be less massive and/or less resilient and/or eachcarry less load, than the single spring assembly associated with theother lever carrying only one wheel). For example, the two springassemblies associated with the two wheels may be provided on oppositesides of the bracket, for example one assembly mounted on one plate onone side of the bracket and the other spring assembly being mounted onthe other plate on the opposite side of the bracket.

It will be noted that the shape of the bracket 3014 is the same as thebracket 14 of FIGS. 1 and 2. In these respective embodiments, the sameshape, size, and material is used. The multiple applications to whichthe same part (the bracket) can be used may lead to the part havingredundant mass or other features when used in one application (greaterredundant mass typically being viewed very negatively in aircraftdesign) but the part having the great benefit of forming part of amodular kit for landing gear design and manufacture. It will be seenthat a mounting point and its associated hole (labelled 3028 r in FIG.6) is redundant. A comparison of the relative loads expected to betransmitted into the aircraft illustrated schematically by the arrows atthe top of FIGS. 2 and 6 shows that the expected load 3040 at the farfore end of the hinge portion of the bracket 3014 of FIG. 6 is less thanthe expected load 3042 at the far aft end; whereas when compared to thespread of loads shown in FIG. 2, the relative loads 40, 42 at the farfore end and the far aft end are similar in magnitude. The mass andshape of the hinge portion of the bracket as compared between FIGS. 1and 5 is very similar (optimally substantially the same).

The modular landing gear bracket thus facilitates the move from atwo-wheel gear design gear to a three-wheel gear design, without adisproportionate increase in mass, without a disproportionate change instructure and without a disproportionate amount of redesign workrequired. The use of a three-wheel gear design is also one that is notcommon in the aircraft industry, it often being the case that aircraftmanufactures favour (possibly as a prejudice in the art) adding wheelsin pairs to landing gear assemblies if and when an aircraft is to bedesigned and manufactured using a previous aircraft design needing fewerwheels. Thus, the conventionally accepted practice of adding two wheelsto the main landing gears when designing a new aircraft, that has ahigher MTOW than the base-level design having two main landing gearseach with only two wheels, can add a significant mass to the aircraft,in terms of the wheels, tyres and associated brakes alone (total mass ofmore than 250 Kg per wheel being typical). If two wheels are added (tomake two main landing gears each with three wheels) rather than addingfour wheels, there is the potential for a mass saving of more than 500Kg, which would make a very large operational saving over the lifetimeof the aircraft.

Thus, the subject matter embodied by FIG. 5 may be described in moregeneral terms as being an aircraft landing gear assembly comprising alanding gear bracket, preferably a modular bracket, on which a firstlever and a second lever are mounted, one for receiving two wheels inside-by-side configuration (e.g. in a diablo configuration) and theother for receiving a single wheel, thus providing a three-wheel landinggear assembly. There are various preferred features relating to thisgeneralised subject matter which will now be described. The landing gearbracket may have a hinge portion, a first mounting point, a secondmounting point, and a third mounting point in a manner similar to thatdescribed above in relation to the general subject matter embodied byFIG. 4. The single wheel may be positioned in-line with the bracket, forexample so that the centre plane of the single wheel is substantiallycoplanar with the corresponding centre plane of the bracket and/or liesin the middle of the two centre planes of the wheels that are arrangedside-by-side. One or more shock absorbers may be provided, for examplethere being greater shock absorbing capacity associated with the levercarrying two wheels than the shock absorbing capacity associated withthe other lever carrying the single wheel. There may be more separateshock absorbers associated with the lever carrying two wheels than thenumber of shock absorbers associated with the other lever. A balance armmay be provided (see further explanation below) which may be mounted forrotation relative to the bracket for reacting, on one side of the arm,the loads from the fore wheel(s) and, on the other side of the arm, theloads from the aft wheel(s).

FIG. 7 shows a three-wheel landing gear assembly according to anembodiment similar to that shown in FIGS. 5 and 6 (and also to FIGS. 1and 2). Like reference numerals are used for like parts, but adding 4000to the numbers used in FIGS. 1 and 2. The main differences between thetwo three-wheel embodiments will now be described. The bracket 4014 isshorter in the fore-aft direction at its upper end, in that the hingeportion is shorter. The loads transmitted into the aircraft body aretherefore more concentrated (in the fore-aft direction). In a variationof this embodiment, the hinge portion is the same length and the bracket4014 has a substantially identical shape as in FIG. 1. The bracket 4014also uses a shock absorber and linkage system 4050 instead of one ormore spring assemblies. As such the structure providing the stops thatinteract with the spring system as shown in FIG. 1 (which stop structuremay be modular—and separately removable—in any case) is not present inthe embodiment of FIG. 7. The shock absorber and linkage system 4050comprises a link 4052 pivotally mounted to the fore lever 4016 f at oneend and pivotally mounted at the other end to a fore end of the balancearm 4054 at a fore pivot point 4054 f. A principal pivot point of thebalance arm 4054 is pivotally mounted at a mounting point 4056 on thebracket near the middle of the bracket as viewed in FIG. 7. A shockabsorber 4058, pivotally mounted to the aft lever 4016 a at one end, ispivotally mounted at the other end to the aft end of balance arm 4054(at an aft pivot point 4054 a). Greater loads are expected at the aftend of the balance arm 4054 as a result of the loads transferred fromthe two aft wheels 4022 a as compared to the loads expected at the foreend of the balance arm 4054 from the loads transferred from the singlefore wheel 4022 f. To better balance the moments on the balance arm itis mounted in an offset position such that point on the balance armcorresponding to the mounting point 4056 is positioned off-centre andcloser to the aft mounting point 4054 a on the balance arm. The loads onthe wheels should therefore be more evenly distributed and the loadsinto the aircraft may be better distributed.

Thus, the subject matter embodied by FIG. 7 may be described in moregeneral terms as being an aircraft landing gear assembly comprising anaircraft landing gear assembly comprising a landing gear bracket,preferably a modular bracket, on which a first lever and a second leverare mounted, one for receiving two wheels and the other for receiving asingle wheel, thus providing a three-wheel landing gear assembly,wherein a balance arm is provided for reacting and/or transmitting thediffering loads received from the wheels. The balance arm may, forexample, be mounted for rotation about a point which is offset from themidway point between the point at which the fore wheel(s) loads arereceived at the arm and aft wheel(s) loads are received at the arm. Itmay be that the loads from the first and second levers are unequalloads, for example. There are various preferred features relating tothis generalised subject matter which will now be described. The landinggear bracket may have a hinge portion, a first mounting point, a secondmounting point, and a third mounting point in a manner similar to thatdescribed above in relation to the general subject matter embodied byFIG. 4. The arm has a fore end pivot point connected to a lever via oneor more link members which transmit loads received from the lever. Thearm has an aft end pivot point connected to a lever via one or more linkmembers which transmit loads received from the lever. The two wheels onthe one lever may be provided in a side-by-side configuration (e.g. in adiablo configuration). The first lever may have a first end which isrotatably mounted to the bracket at the first mounting point and asecond end, positioned forward of the first end, for receiving anaircraft wheel. The second lever may have a first end which is rotatablymounted to the bracket (e.g. at the first mounting point) and a secondend, positioned rearward of the first end, for receiving a secondaircraft wheel.

FIG. 8 shows a landing gear assembly according to an embodiment similarto that shown in FIG. 7. Like reference numerals are used for likeparts, but starting with a “5” not a “4” as in FIG. 7 (adding 5000 tothe numbers used in FIGS. 1 and 2). The main differences will now bedescribed. The landing gear carries four wheels 5022, with a similarlysized bracket 5014, but using an extra shock absorber. There are thustwo shock absorbers: a fore shock absorber 5058 f and an aft shockabsorber 5058 a, each pivotally mounted at opposite ends 5054 a, 5054 fof the balance arm 5054. In this embodiment, the balance arm is mountedat a centre point 5056 to the bracket 5014 which is located midway (orvery close to midway) between the aft mounting point 5054 a and the foremounting point 5054 f on the balance arm. The fore shock absorber 5058 fis a high pressure shock absorber (transferring high load for a giveneffective surface area), whereas the aft shock absorber 5058 a is a lowpressure absorber. The linkage assembly comprising the two segregatedand different shock absorbers, and the balance arm, is thus able to actas a two-stage shock absorbing system for the four wheels. In avariation of the embodiment, there are three wheels, and the two shockabsorbers are both at substantially the same pressure, but the oleo areaof the shock absorber associated with the single wheel is half that ofthe oleo area of the shock absorber associated with the dual wheels.

Thus, the subject matter embodied by FIG. 8 may be described in moregeneral terms as being an aircraft landing gear assembly comprising anaircraft landing gear assembly comprising a landing gear bracket,preferably a modular bracket, on which first and second levers aremounted for receiving two or more wheels between them, a balance armpivotally mounted on the bracket the balance arm being connected, viaone or more link members and/or shock absorbers for example, forreacting and/or transmitting ground loads received from the wheels.There are various preferred features relating to this generalisedsubject matter which will now be described. The landing gear bracket mayhave a hinge portion, a first mounting point, a second mounting point,and a third mounting point in a manner similar to that described abovein relation to the general subject matter embodied by FIG. 7. Thebalance arm is rotatably mounted on the bracket via a middle pivotpoint, the arm having a fore end pivot point connected to the firstlever via one or more link members and an aft end pivot point connectedto the second lever via one or more link members. One or more of thelink members may comprise a shock absorber. The one or more link membersconnecting the first lever to the balance arm may comprise the firstshock absorber (which therefore transmits loads received from the firstlever). Similarly, the one or more link members connecting the aft endpivot point of the arm to the second lever may comprise the second shockabsorber (which therefore transmit loads received from the secondlever). The balance arm may thus be connected at either end to arespective shock absorber. One of the first and second shock absorbersis a low pressure shock absorber, the other being a high pressure shockabsorber. (The terms low pressure shock absorber and high pressure shockabsorber are relative and convey the meaning merely that the pressure ofthe low pressure shock absorber is lower than the pressure of highpressure shock absorber; rather than placing any absolute limits on theoperating pressure of either the low pressure shock absorber or the highpressure shock absorber.)

FIG. 9 shows a landing gear assembly according to an embodiment similarto that shown in FIG. 7. Like reference numerals are used for likeparts, but starting with a “6” not a “4” as in FIG. 7 (adding 6000 tothe numbers used in FIGS. 1 and 2). The main differences will now bedescribed. The landing gear 6010 carries two wheels 6022, with a rakedbracket 6014 having a wing-mounted hinged portion 6018. Loads aretransmitted into the wing from the bracket 6014 at two points. (It willbe appreciated that there may be a side stay—not shown—additionally).The bracket 6014 has a shock absorber and linkage system 6050, but inreverse configuration with the link 6052 pivotally mounted to the aftlever 6016 a at one end and pivotally mounted at the other end to theaft end of the balance arm 6054 at the aft pivot point 6054 a. The shockabsorber 6058 is pivotally mounted to the fore lever 6016 f at one endand pivotally mounted at the other end to the fore end of balance arm6054 (at the fore pivot point 6054 f). The principal pivot point of thebalance arm 6054 is centrally located relative to the aft pivot point6054 a and the fore pivot point 6054 f. The principal pivot point of thebalance arm 6054 is however located off-centre (to the aft side) of thebracket and also rearward of the aft mounting point 6026 of the hingeportion 6018 of the bracket 6014. The bracket is raked and thus has atrailing wheel configuration. The rake angle is, in this embodiment,defined as the angle to the vertical of the notional line that extendsbetween the first mounting point 6020 on the bracket to the rearmostmounting point (the third mounting point 6026) on the bracket 6014. Therake angle shown in FIG. 9 according to this definition is greater than15 degrees, and significantly greater than 6 degrees, which might beviewed as the maximum practical angle by which an oleo cylinder of aconventional landing gear leg could be raked. The embodiment of FIG. 9may have particular application in relation to an aircraft havingextended wing tips (e.g. for increased aerodynamic efficiency). Suchwings have a mean aerodynamic chord which is longer, which has theeffect of requiring the main landing gear wheels to shift aft, whichmeans that the wheels end up further away from the rear spar (in thefore-aft direction). Utilising the lever assembly shown in FIG. 9 allowsa shock absorber to be used at a greater range of angles to thevertical, thus allowing the landing gear assembly to have an effectiverake angle that is much higher than previously possible with theconvention landing gear designs. A variant of this embodiment is a 3wheel option.

Thus, the subject matter embodied by FIG. 9 may be described in moregeneral terms as being an aircraft wing landing gear assembly comprisinga raked landing gear bracket, preferably a modular landing gear bracket,extending from a hinge portion to a point, at which one or more leversare mounted for carrying one or more wheels, and a link assemblyincluding a shock absorber (optionally arranged when the wheels aredeployed so that the shock absorber axis is at an angle that is greaterthan 8 degrees to the vertical) which, in use, transmits at least someof the ground loads from at least one of the levers into the bracket.There are various preferred features relating to this generalisedsubject matter which will now be described. The landing gear bracket mayhave a hinge portion, a first mounting point, a second mounting point,and a third mounting point in a manner similar to that described abovein relation to the general subject matter embodied by FIG. 7. There maybe a first lever having a first end which is rotatably mounted to thebracket at the first mounting point and a second end, positioned forwardof the first end, for receiving a first aircraft wheel in a positionoutboard of the first lever; and a second lever having a first end whichis rotatably mounted to the bracket at a mounting point (which may bethe same as the first mounting point or which may be displacedtherefrom) and a second end, positioned rearward of the first end, forreceiving a second aircraft wheel. One or both of the first and secondlevers may carry two wheels. The bracket may be raked in that, in use,when the aircraft is static and on the ground the first mounting pointis located aft of the third mounting point. Alternatively, oradditionally, the bracket may be raked such that, in use, when theaircraft is static and on the ground the rake angle is eight degrees orhigher (e.g. greater than ten degrees). The rake angle may beself-evident in the geometry of the bracket. If not, or alternatively,the rake angle may be defined by the angle to the vertical defined bythe notional line extending from the first mounting point (or if thereare multiple levers carrying wheels, the mean average position of theirmounting points on the bracket) to the third mounting point (and/or ifthere are three of more mounting points at the hinge portion, therearmost of those hinge portion mounting points). The shock absorber ofthe link assembly may be the largest (or equal largest) of the shockabsorbers associated with the landing gear concerned.

FIG. 10 shows a variation of the embodiment shown in FIGS. 1 and 2. Likereference numerals are used for like parts, but starting with a “7”(adding 7000 to the numbers used in FIGS. 1 and 2). The main differenceswill now be described. The bracket 7014 has a shorter (in thelongitudinal direction) hinge portion 7018. The bracket 7014 has, at itsupper end as shown in FIG. 10) only two mounting points for mounting ofthe bracket 7014 to the aircraft structure 7012 and a single mountingpoint 7020 (the “first mounting point”) at its lower end. Thus, thesecond mounting point 7024 is at the front of the hinge portion 7018 andthe third mounting point 7026 is at the rear of the hinge portion. Theoverall shape of the bracket is less triangular than the FIG. 1embodiment, because the upper part of the bracket of FIG. 10 is shorter(in the longitudinal direction) without being very differently shapedfrom the bracket of FIG. 1 at its lower end.

FIG. 11 shows a different variation of the embodiment shown in FIGS. 1and 2. Like reference numerals are used for like parts, but startingwith an “8” (adding 8000 to the numbers used in FIGS. 1 and 2). The maindifferences will now be described. The hinge portion 8018 of the bracket8014 is provided by two spaced apart tubular sections 8019, rather thana single tube as shown in FIG. 2, each tubular section 8019 beingintegrally formed as part of the bracket 8014. The bracket 8014 has, atits upper end as shown in FIG. 11) only two mounting points for mountingof the bracket 8014 to the aircraft structure 8012 and a single mountingpoint 8020 (the “first mounting point”) at its lower end. Thus, thesecond mounting point 8024 is at the front of the hinge portion 8018 andthe third mounting point 8026 is at the rear of the hinge portion. Itwill be seen that the second and third mounting points 8024, 8026 arefurther apart in FIG. 11 than the corresponding points in FIG. 10.

It will be seen that the collection of the above-described embodiments,modifications thereof and similar non-illustrated embodiments, utilise acommon design principle that not only deviates from the conventionalstructure and configuration of aircraft landing gear designs but alsoprovides a common platform facilitating a method of designing andmanufacturing a new landing gear making use of a modular design system.FIG. 10 shows a method (illustrated by flowchart 500) of manufacturing alanding gear assembly utilising such a design method. There is a step(box 501) of designing a first aircraft landing gear assembly for afirst aircraft, the first aircraft having a fuselage of a first lengthand having a first MTOW. There is a step (box 502) of designing a secondaircraft landing gear assembly for a second aircraft, the secondaircraft having a fuselage of a second longer length and having a secondhigher MTOW. Step 501 may be conducted before, after, or in parallelwith step 502 or overlap in part with step 502. The first aircraftlanding gear assembly may for example be either a two-wheel tandemlanding gear assembly or a two-wheel diablo landing gear assembly. Thefirst aircraft landing gear assembly comprises a load-bearing frame (forexample, a modular bracket as described herein) moveable between adeployed position and a stowed position. In the deployed position, theload-bearing frame may support the majority (e.g. 75% or substantiallyall) of the landing gear loads when the aircraft is stationary on theground. The load-bearing frame has features and/or mass that is/areredundant for the purpose of operation of the first aircraft (e.g.redundant in the sense that their absence would not affect the validcertification of the aircraft for commercial operation). The secondaircraft landing gear assembly comprises a similar (or identical)load-bearing frame also moveable between a deployed position and astowed position. The steps 501, 502 are carried out such that thefeatures or mass of the load-bearing frame of the first aircraft landinggear assembly that are redundant for the purpose of operation of thefirst aircraft are used as features or mass of the load-bearing frame ofthe second aircraft landing gear assembly that are utilised (and/ornecessary) for the purpose of operation of the second aircraft (forexample, necessary for effective and efficient operation of the secondaircraft and/or necessary for certification or safety purposes). Forexample, the load-bearing frame may comprise redundant structure, whichis surplus to requirements for operation of the aircraft on which theaircraft landing gear assembly is to be used, the redundant structurecomprising one or more of an additional mounting point (e.g. for alinkage assembly as described above) and additional mass fortransmitting loads. It will be understood that the load-bearing frame(or bracket) has redundant features that are redundant in a sense otherthan providing redundancy solely as a structural failsafe. There thenfollows a step (box 503) of making at least one of the first and secondaircraft landing gear assemblies. Optionally, there is a step (box 504)of making the other of the first and second aircraft landing gearassemblies (possibly before, after, during and/or overlapping with step503). It may be that the second aircraft landing gear assembly has adifferent topology/geometry of the wheel—frame arrangement. For example,it may be that the first aircraft landing gear assembly is a two-wheeltandem landing gear assembly and the second aircraft landing gearassembly is a two-wheel diablo landing gear assembly. Alternatively, itmay be that the first aircraft landing gear assembly is a two-wheeldiablo landing gear assembly and the second aircraft landing gearassembly is a two-wheel tandem landing gear assembly. As a furtheralternative, it may be that the second aircraft landing gear assemblyhas three or more wheels. There are various preferred features relatingto this generalised subject matter which will now be described. Thelanding gear load-bearing frame may have a hinge portion, a firstmounting point, a second mounting point, and/or a third mounting pointin a manner similar to that described above in relation to the generalsubject matter embodied by FIG. 7. The landing gear may have featuresdescribed with reference to the any of the previously describedembodiments. It may be that one of the first and second aircraft landinggear assemblies is a design modification of the other. A designmodification may be considered as a design which is based on the earlierdesign and uses the earlier design as the principal starting point forthe new design (being a design modification). It may also be the casethat each of the above mentioned first and second aircraft landing gearassemblies is a design modification in that both utilise a commongeneric design model. The common generic design model may becommon/generic in the sense that the loading of the landing gear(principal load paths) are the same, at least for certain parts of thecommon design. The load-bearing frame/bracket may be the same shapeand/or geometry and/or perform the same overall function. The commongeneric design model may be common/generic in the sense that embodimentsof the common generic design model would be considered equivalent underthe concept of the doctrine of equivalent under US patent law. Having acommon generic design model when designing a new landing gear assemblymay significantly speed up and simplify the design and then subsequentmanufacture of the landing gear assembly such that even if a version ofa new landing gear assembly designed with the common generic designmodel is slightly heavier than it might otherwise need to be, that is aprice worth paying in view of the efficiencies gained elsewhere.

Whilst the present invention has been described and illustrated withreference to particular embodiments, it will be appreciated by those ofordinary skill in the art that the invention lends itself to manydifferent variations not specifically illustrated herein. By way ofexample only, certain possible variations will now be described.

In some embodiments, one or each of the first and second spring elements(e.g. parts 131, 132) may comprise a composite spring. By compositespring, it is meant a spring made from a combination of materials, suchas metal and carbon. In some other embodiments, one or each of the firstand second spring elements may be made from a single material, such as asingle metal or metal alloy. In some embodiments, the first springelement could comprise a bell crank, with the first and second endportions forming the arms of the bell crank.

In other embodiments, the second spring element may be mounted orattached to the bracket in a non-pivotal manner For example, the secondspring element may be clamped in position relative to the bracket.

In some embodiments, the second stop may be omitted. In thoseembodiments, rotation of the end portion of the first spring elementabout the mounting point (e.g. labelled 28) during removal or reductionof that load may be controlled or limited by the second spring element.

The hinge portion of the bracket may comprise further mounting pointswhich, in use, transfer loads into the aircraft structure (e.g. wing orfuselage).

The landing gear of the above embodiments, may be a main landing gearwhich is body-mounted. In other embodiments, the landing gear may be amain landing gear that is wing-mounted. In a further variation, anaircraft may comprise two or more main landing gear that are eachaccording to different embodiments of the present invention. The landinggear of the above embodiments, may be a nose landing gear.

The aircraft in which the landing gear is mounted may be different fromthat shown in FIG. 3.

The hinge portion of the landing gear may have only two attachmentpoints/mounting points for hinging the landing gear relative to theaircraft. Each attachment point may be associated with a respectivepintle.

When designing a bracket for use on a lighter aircraft and a heavieraircraft, one could choose to optimise the weight of the bracket for thelower weight variant, with the overall shape and geometry of mountingpoints being the same for the heavyweight variant, but with greatermass. This could lead to one-way interchangeability (changing alightweight bracket for a heavyweight bracket would be permitted on alower weight variant aircraft, but the lightweight bracket would not bepermitted for use on the heavyweight variant aircraft). This could havesome advantage for spares holding (e.g. it would be sufficient to stockonly the heavyweight bracket as a spare).

Where in the foregoing description, integers or elements are mentionedwhich have known, obvious or foreseeable equivalents, then suchequivalents are herein incorporated as if individually set forth.Reference should be made to the claims for determining the true scope ofthe present invention, which should be construed so as to encompass anysuch equivalents. It will also be appreciated by the reader thatintegers or features of the invention that are described as preferable,advantageous, convenient or the like are optional and do not limit thescope of the independent claims. Moreover, it is to be understood thatsuch optional integers or features, whilst of possible benefit in someembodiments of the invention, may not be desirable, and may therefore beabsent, in other embodiments. The term ‘or’ shall be interpreted as‘and/or’ unless the context requires otherwise.

1. A modular aircraft landing gear assembly, wherein the modularaircraft landing gear assembly comprises: a modular landing gear bracketextending from a hinge portion to a first mounting point, the hingeportion being configured for mounting the bracket for rotation relativeto a landing gear bay, and the first mounting point being for receivinga ground load from one or more wheels, in use, the modular landing gearbracket including a second mounting point at a fore location of thehinge portion and a third mounting point at an aft location of the hingeportion, the bracket being configured so that the ground load receivedat the first mounting point is, in use, transferred into aircraftstructure via the second mounting point and the third mounting point, alever having a first end which is rotatably mounted to the bracket atthe first mounting point and a second end for receiving a first aircraftwheel, structure for receiving a second aircraft wheel, a linkageassembly, the linkage assembly in use transmitting at least some of theground load via at least one of a spring and a shock absorber, whereinthe modular landing gear bracket comprises redundant structure, which issurplus to requirements for operation of the aircraft on which theaircraft landing gear assembly is to be used, the redundant structurecomprising one or more of an additional mounting point and additionalmass for transmitting loads.
 2. A modular aircraft landing gear assemblyaccording to claim 1, wherein the modular aircraft landing gear assemblyis configured for a two-wheel configuration, and wherein the redundantstructure facilitates reconfiguring the modular aircraft landing gearassembly for use with more wheels.
 3. A modular aircraft landing gearassembly according to claim 1, wherein the structure for receiving asecond aircraft wheel includes a second lever, which has a first endwhich is rotatably mounted to the bracket and a second end for receivingthe second aircraft wheel, and wherein one of the first and secondlevers is positioned behind the other in the fore-aft direction.
 4. Amodular aircraft landing gear assembly according to claim 3, wherein theaircraft wheel of one of the first and second levers is, in use with theaircraft on the ground, located to one side in an outboard direction ofthe mid-plane of the bracket, and the other of the first and secondlevers is configured to receive the second aircraft wheel so that it iseither positioned in-line with the first wheel or located to one side inan inboard direction of the mid-plane of the bracket.
 5. A modularaircraft landing gear assembly according to claim 3, wherein theredundant structure of the bracket is provided to enable the bracket tocarry three wheels, two being arranged in diablo configuration and onebeing arranged either forward of or behind the two wheels.
 6. A modularaircraft landing gear assembly according to claim 1, the modularaircraft landing gear assembly further including a balance arm rotatablymounted on the bracket via a middle pivot point, the arm having a foreend pivot point connected to the first lever via one or more linkmembers which transmit loads received from the first lever, the armhaving an aft end pivot point connected to the second lever via one ormore link members which transmit loads received from the second lever.7. A modular aircraft landing gear assembly according to claim 6,wherein the middle pivot point of the balance arm is offset from theposition midway between the fore end pivot point and the aft end pivotpoint.
 8. A modular aircraft landing gear assembly according to claim 1,further including a first shock absorber which transmits loads from thefirst lever.
 9. A modular aircraft landing gear assembly according toclaim 8, further including a second shock absorber which transmits loadsfrom the second lever.
 10. A modular aircraft landing gear assemblyaccording to claim 9, wherein one of the first and second shockabsorbers is a low pressure shock absorber and the other of the firstand second shock absorbers is a high pressure shock absorber.
 11. Amodular aircraft landing gear assembly according to claim 1, wherein thebracket is raked such that, in use, when the aircraft is static and onthe ground the first mounting point is located aft of the third mountingpoint.
 12. A modular aircraft landing gear assembly according to claim1, wherein the linkage assembly comprises a loading point which ismovable relative to the hinge portion of the bracket, the loading pointin use receiving ground load from the first lever.
 13. A modularaircraft landing gear assembly according to claim 1, wherein the linkageassembly comprises a spring system that is configured to apply aresilient biasing force acting against the ground loads so that, duringapplication of an increasing load, the spring rate of the spring systemchanges in dependence on the load being transmitted.
 14. A modularaircraft landing gear assembly according to claim 1, wherein the linkageassembly is pivotally mounted via a fourth mounting point of thebracket, and the modular landing gear bracket includes a fifth mountingpoint for the mounting of a further linkage assembly, to be positionedeither fore or aft of the linkage assembly pivotally mounted via thefourth mounting point.
 15. (canceled)
 16. (canceled)
 17. (canceled) 18.A method of manufacturing a landing gear assembly, wherein the methodincludes designing both (a) a first aircraft landing gear assembly for afirst aircraft, the first aircraft having a fuselage of a first lengthand having a first MTOW and (b) a second aircraft landing gear assemblyfor a second aircraft, the second aircraft having a fuselage of a secondlonger length and/or having a second higher MTOW, the first aircraftlanding gear assembly comprising a load-bearing frame moveable between adeployed position in which it supports the majority of the landing gearloads when the aircraft is stationary on the ground, and a stowedposition, the second aircraft landing gear assembly comprising aload-bearing frame moveable between a deployed position in which itsupports the majority of the landing gear loads when the aircraft isstationary on the ground, and a stowed position, and then making atleast one of the first and second aircraft landing gear assemblies, andwherein (i) the load-bearing frame has features and/or mass that is/areredundant for the purpose of operation of the first aircraft, and thefeatures or mass of the load-bearing frame of the first aircraft landinggear assembly that are redundant for the purpose of operation of thefirst aircraft are used as features or mass of the load-bearing frame ofthe second aircraft landing gear assembly that are utilised for thepurpose of operation of the second aircraft, and/or (ii) theload-bearing frame of the second aircraft has the same geometry as theload-bearing frame of the first aircraft but is scaled up and/or theload-bearing frame of the second aircraft has the same shape as theload-bearing frame of the first aircraft but is strengthened by use ofextra mass in the structure of the load-bearing frame.
 19. (canceled)20. An aircraft landing gear assembly comprising: a modular landing gearbracket extending from a hinge portion to a first mounting point, thehinge portion being configured for mounting the bracket for rotationrelative to a landing gear bay, and the first mounting point being forreceiving a ground load from one or more wheels, in use, the bracketincluding a second mounting point at a fore location of the hingeportion and a third mounting point at an aft location of the hingeportion, the bracket being configured so that the ground load receivedat the first mounting point is, in use, transferred into aircraftstructure via the second mounting point and the third mounting point, afirst lever having a first end which is rotatably mounted to the bracketat the first mounting point and a second end, positioned forward of thefirst end, for receiving a first aircraft wheel, and a second leverhaving a first end which is rotatably mounted to the bracket at thefirst mounting point and a second end, positioned rearward of the firstend, for receiving a second aircraft wheel.
 21. An aircraft landing gearassembly according to claim 20, wherein one of the first lever and thesecond lever is configured to carry two wheels in a diabloconfiguration, and the other of the first lever and the second lever isconfigured to carry a single wheel.
 22. An aircraft landing gearassembly according to claim 20, further comprising a balance armrotatably mounted on the bracket via a middle pivot point, the armhaving a fore end pivot point connected to the first lever via one ormore link members which transmit loads received from the first lever,the arm having an aft end pivot point connected to the second lever viaone or more link members which transmit loads received from the secondlever, and the middle pivot point of the balance arm being offset fromthe position midway between the fore end pivot point and the aft endpivot point.
 23. An aircraft landing gear assembly according to claim20, further comprising a balance arm rotatably mounted on the bracketvia a middle pivot point, the arm having a fore end pivot pointconnected to the first lever via one or more link members include afirst shock absorber, the arm having an aft end pivot point connected tothe second lever via one or more members comprising a second shockabsorber which transmit loads received from the second lever, one of thefirst and second shock absorbers being a low pressure shock absorber andthe other of the first and second shock absorbers being a high pressureshock absorber.
 24. An aircraft wing landing gear assembly according toclaim 20, further comprising a linkage assembly, the linkage assembly inuse transmitting at least some of the ground load via at least one of aspring and a shock absorber, wherein the bracket is raked such that, inuse, when the aircraft is static and on the ground the first mountingpoint is located aft of the third mounting point and/or defines a rakeangle of eight degrees or higher.
 25. An aircraft wing landing gearassembly according to claim 24, wherein the bracket is raked such that,in use, when the aircraft is static and on the ground the rake angledefined by the notional line extending from the first mounting point tothe third mounting point is eight degrees or higher.
 26. An aircraftwing landing gear assembly according to claim 24, wherein the secondlever is rotatably mounted to the bracket at a further mounting pointand the bracket is raked such that, in use, when the aircraft is staticand on the ground the rake angle defined by the notional line extendingfrom the midway point between the mounting points on the bracket of thefirst and second levers to the third mounting point is eight degrees orhigher.
 27. An aircraft landing gear assembly according to claim 20,wherein one of the first and second wheels being in a position locatedto one side in an outboard direction of the mid-plane of the bracket andthe other of the first and second wheels either being in a positionlocated to the one side in an inboard direction of the mid-plane of thebracket or in-line with the first wheel.